[aprssig] Low-cost weather station

Scott Miller scott at opentrac.org
Sat Mar 29 10:15:55 EDT 2008

> 1)  Durability - will they be reliable?
> When a big blow renders an anemometer dead, at a remote site,
> it may likely be dead for quite a while.  Then the question arises
> as to whether it's financially wise to replace it.

That remains to be seen.  I've spun the anemometer up to about 100 mph 
with an air compressor and it doesn't fly apart, at least.  It seems 
more durable to me than the LaCrosse anemometer I've got on the roof 
now.  It's not going to compare with a high-end station for long-term 
durability, of course, but not everyone needs that.

> 2)  How is the accuracy?
> How do the sensors compare to the typical, low-end consumer grade stuff
> (Peet, Davis, etc).

There's not a lot to the sensors themselves - the mechanical ones, 
anyway.  And I can select whatever temperature, humidity, and baro 
sensors I want for the rest of it.

The original station doesn't measure wind speed very well at low rates, 
possibly because of too short an integration period.  Aside from the air 
compressor testing, I also took the anemometer off and injected a signal 
from a function generator to simulate different speeds.  It was linear 
above about 10 mph, but a large amount of jitter below that speed tells 
me it wasn't keeping a very long count.  None of that matters in my 
application, because again, I'll be handling that part.

> 3)  Is there any provision for upgrading due to changes in things like
> WMO reporting requirements?  I suspect, like most other low end stuff,
> It's pre-programmed and cannot be changed.  Most likely, it doesn't
> Conform to current NWS/WMO standards.  Most folks don't care, but I

Upgrading what?  The mechanical sensors?

> 4)  Are there provisions for calibrating these sensors.  Especially
> baro?
> Software offsets... maybe I expect too much.

I'll certainly provide a mechanism to set calibration factors.

> 5)  Scott, will you assume responsibility for US customer support,
> warranty
> replacement, all that??

Yeah, the finished system will be my product.

I don't expect it to take the place of a high-end system, but I think 
it'll be especially attractive for places where you might otherwise use 
the AAG station and just need wind and temperature data.  Hang 
glider/paraglider flight areas (especially when vandalism or accidental 
damage is a major risk) for example.  If you need a station that'll run 
for 10 years with no maintenance in a place that gets 100 mph wind and 
freezing rain, this is NOT the station you want.

Here's a drawing of the same sensor assembly - I won't be getting it 
with the transmitter module that goes in the pagoda.



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